Sin in Particle in a Box

[Melissa Hua 3G]

Why do they use the sin function for the particle in a box example? I also don't particularly understand the equation put in the book.

[706244927]

To describe the wave of the electron you have to use a wave function that properly describes the motion of the particle.

A sine wave starts at zero amplitude and ends at zero amplitude just as the wave of a particle inside a box does.